Amateur radio enthusiasts use various modulation types to transmit information over the airwaves. Here are some of the common ones that you will use on HF radios
- Amplitude Modulation (AM): AM is one of the oldest modulation techniques. In AM, the amplitude of the carrier wave is varied in proportion to that of the message signal being transmitted. It’s relatively simple but less efficient in terms of bandwidth usage compared to other modulation types.
- Frequency Modulation (FM): In FM, the frequency of the carrier wave is varied in accordance with the amplitude of the modulating signal. FM is known for its resistance to amplitude variations caused by noise and interference, making it suitable for high-quality audio transmissions.
- Single-Sideband Modulation (SSB): SSB is a form of amplitude modulation where only one of the sidebands is transmitted, along with the carrier wave. This technique effectively utilizes bandwidth and power, making it popular for long-distance communication in amateur radio.
- Continuous Wave (CW): Also known as Morse code, CW involves the continuous transmission of a carrier wave with varying signal interruptions to represent letters, numbers, and punctuation. It’s highly efficient in terms of bandwidth usage and is still widely used by amateur radio operators.
- Phase Modulation (PM): In PM, the phase of the carrier wave is varied in proportion to the modulating signal. It’s similar to FM but varies the phase instead of frequency. PM is less common in amateur radio but has applications in certain digital modulation techniques.
- Digital Modulation: Various digital modulation techniques are used in amateur radio, including:
- Binary Phase Shift Keying (BPSK): Modulates the phase of the carrier wave to represent binary data.
- Quadrature Phase Shift Keying (QPSK): Similar to BPSK but with four phase shifts, allowing for higher data rates.
- Frequency Shift Keying (FSK): Modulates the frequency of the carrier wave to represent digital data.
- Amplitude Shift Keying (ASK): Modulates the amplitude of the carrier wave to represent digital data.
These modulation types enable amateur radio operators to communicate over various distances and under different conditions, depending on factors like frequency band, atmospheric conditions, and available equipment.
